The present invention relates to crane sheave assemblies used for load lifting. The purpose of the present invention is to address sheave assembly removal problems found in the current art.
Currently, cranes are designed having a number of possible boom tops. Specific boom tops are used depending on the type of lift required. Typically, there are boom top designs for normal liftcrane work, for heavier loads and for lighter loads that must be lifted from a greater distance.
All crane boom tops have sheave assemblies, over which the lift rope is carried. The currently available crane sheave assemblies consist of sheaves mounted on continuous through-shafts. Typically, sheave assemblies differ only by the number of sheaves contained therein. The heavier the load required to be lifted by the crane, the greater the number of sheaves required in the sheave assembly. Since sheave assemblies are self-contained units, crane operators must purchase that sheave assembly with the minimum number of sheaves required to perform the lift.
A limited number of sheave assembly designs are available from which crane operators may choose. Therefore, often, the sheave assembly will contain more sheaves than is necessary to perform a particular lift. These extra sheaves constitute unnecessary weight on the crane boom top which, in turn, necessitate additional crane counterweight in order to maintain crane stability. Keeping the crane boom top as light as possible maximizes the boom length that can be used and load that can be raised, and minimizes the crane counterweight required. Usually, however, because of the current difficulty in removing individual sheaves from sheave assemblies, unnecessary sheaves are not removed and the crane operator instead operates the crane with a shorter boom or increased crane counterweight. Thus, it would be advantageous to design a sheave assembly from which unnecessary sheaves could be easily removed.
Similarly, if individual sheaves in the sheave assemblies require repair or replacement, the entire through-shaft must be detached from the crane boom top and successive sheaves removed from the shaft until the target sheave is reached. This inevitably results in the need for the sheaves to be repositioned and realigned on the through-shaft. Oftentimes, this procedure causes sheave bearings to be damaged.